Egg freezing had long been labeled experimental, but the American Society for Reproductive Medicine declared that's no longer the case. The group cited studies that found younger women are about as likely to get pregnant if they used frozen-and-thawed eggs for their infertility treatment as if they used fresh ones.

The move is expected to help cancer patients preserve their fertility, by pushing more insurers to pay for their procedure, and to boost banking of donated eggs, similar to sperm banking.

Here's the controversy: Should otherwise healthy women freeze their eggs as sort of an insurance policy against infertility in case they don't meet Mr. Right — or just aren't ready for motherhood — until their late 30s or beyond, when the childbearing window is closing fast?

The pricey technology, which insurance doesn't cover for elective reasons, is being marketed aggressively for just that use.

Yet the society that represents doctors who treat infertility stopped short of endorsing egg freezing solely for deferring childbearing until women are older. The conclusion: It's not at all clear who's a good candidate, or if women who store their eggs are being given a false sense of security.

"The bottom line is there is no guarantee," said Dr. Samantha Pfeifer of the University of Pennsylvania, who chaired the society's guideline committee. "A lot of women interested in using this technology are in their late 30s, early 40s, and they may have the worst success of anybody."

Anyone considering egg freezing needs careful counseling about their age and the odds of success if they want to later thaw those eggs for use in in vitro fertilization, the guidelines stress.

"It's an insurance policy that many of those women may never need to turn in," added Dr. Eric Widra of Georgetown University, who co-authored the guideline.

But proponents of egg freezing, known medically as oocyte cryopreservation, say lifting the experimental label will encourage more women to check out the option, and they'll make an educated choice.

"It's none of our business to tell someone, 'No, you shouldn't delay childbearing if you choose for whatever reason,'" said Dr. James Grifo of New York University, whose center has frozen more than 1,100 batches of eggs, mostly for elective fertility preservation. "It's not a promise. It's hope and insurance."

For Brigitte Adams of San Francisco, that hope of a future pregnancy was worth paying about $15,000 to freeze 11 eggs, especially when her parents covered half the bill.

"I'm glad I did it when I did it. I wish I had done it a few years earlier," said Adams, who had the procedure about a year ago at age 39. Her doctor estimated she'd have a 30 percent chance of pregnancy using those eggs later on, "and I thought a 30 percent chance was better than a zero chance."

Adams started a web site, eggsurance.com, to spread word of women's experiences with egg freezing. She says one of the most-asked questions is how to learn about clinics' success rates using frozen eggs. Specialists say lifting the experimental label means more clinics will start publicly reporting that information like they do now for other infertility procedures.

Sperm routinely are frozen. So are the extra embryos of couples undergoing infertility treatment, in case they want to use them for later pregnancy attempts.

But eggs proved more delicate and difficult to freeze than sperm or embryos. The problem: Eggs contain lots of water, and early methods of freezing and thawing allowed ice crystals to form that could destroy or damage them. In the past decade, scientists created a flash-freezing method called vitrification that appears to overcome that challenge.

For a number of years, egg-freezing has been offered experimentally for young women or girls who are diagnosed with cancer or other serious illnesses that would destroy their ovaries.

Then there's age-related infertility: About 1 in 5 U.S. women now have their first child after age 35, according to the Centers for Disease Control and Prevention. Yet the ability to conceive begins dropping around 35 and more rapidly as the 40s near. Women have fewer eggs left, and these older remaining ones aren't as healthy, meaning even if the woman can get pregnant she's more likely to miscarry.

What's involved in freezing eggs: Women inject high levels of hormones for a week in order to ovulate as many eggs as possible. Retrieving them is an outpatient procedure that can cost $10,000 to $15,000, sometimes not including the cost of the medication. Clinics also charge a storage fee, and then women who wind up using their eggs will pay thousands more to undergo in vitro fertilization.

There are no estimates of how many women have had their eggs frozen. But Pfeifer's committee cited four well-controlled European studies that compared IVF using either fresh eggs or ones that had been frozen from younger women, and found the chances of pregnancy were comparable.

What about birth defects? There are only about 1,500 known live births resulting from frozen eggs worldwide, compared with about 1 million IVF births using fresh eggs. But a recent review of nearly 1,000 of the births from frozen eggs found no increased risk of birth defects, Pfeifer said.